Device and method for controlling the tension of a weblike material

ABSTRACT

The control device comprises: at least one member ( 12; 12 X) for regulating the speed of advance on the weblike material; a central control unit ( 41 ); a guiding roller ( 31 ) with mobile axis, over which the weblike material is run; and a position transducer ( 39 ) for detecting the position of the guiding roller ( 31 ) and for generating a position signal for controlling the speed of said weblike material. The guiding roller ( 31 ) is supported in a controlled position, and associated thereto is at least one sensor ( 37 ) for detecting a load (F) applied by the weblike material (N) on the guiding roller ( 31 ). In addition, an actuator ( 43 ) controls a displacement of the guiding roller according to a feedback signal generated by the sensor ( 37 ). The actuator is controlled so as to make up for variations of the load of the weblike material by moving the axis of the guiding roller, and the member for regulating the speed of advance of the weblike material ( 5 ) is controlled by said central control unit ( 41 ), according to the position signal, so as to maintain the axis of the guiding roller ( 31 ) in a position that is on average constant.

TECHNICAL FIELD

The present invention relates to an unwinder device for unwinding aweblike material from a reel and feeding it to a processing line at acontrolled tension. More in general, the present invention relates to acontrol device for controlling the tension of a weblike material comingout of a first station and fed to a second station of a processingsystem.

The invention also relates to a method for unwinding a weblike materialfrom a reel and feeding it to a processing line, with an appropriatecontrol of the tension. More in general, the invention relates to amethod for controlling the tension of a weblike material along a feedpath between a first station and a second station set in sequence, withthe possible interposition of further stations, members or devicesbetween them.

BACKGROUND OF THE INVENTION

In multiple industrial fields there arises the need for unwinding aweblike material from a reel for feeding it to a line for transformationor for processing. For example, in the field of paper converting, forthe production of rolls of toilet paper, rolls of paper for domestic orindustrial use, paper handkerchiefs or serviettes, one or more layers ofpaper known as “tissues” are unwound from one or more reels and fed to aline for transformation, which may comprise a rewinder and othermachines arranged in series, to form rolls of a diameter equal to thediameter of the finished product and of large axial length. Said rollsor logs are then cut transversely and divided into a plurality ofsmaller rolls, which are sent on for packaging. Problems similar tothose typical of the field of tissue paper may arise in othertechnological fields, for example in the processing of plastic film,adhesive tape, fabrics, non-wovens, cardboard and in general whereverthere is the need to unwind a weblike material for feeding means orstations for processing.

For unwinding the reels, unwinding devices are used, which provide theunwinding motion to the reel by means of a central mechanism, i.e., onethat transmits motion to the axis of the reel, or else by means of aperipheral mechanism, i.e., one that transmits motion by means of amember (typically a belt), which is in contact with the outer peripheryof the reel. Unwinders of this type are described, for example, inEP-B-0822912 and in U.S. Pat. No. 5,730,389. Other unwinders for weblikematerial are described in GB-A-2294033, U.S. Pat. No. 3,202,376,WO-A-0056644.

The weblike material must be fed to the line for transformation at atension that is substantially constant. This is rendered difficult bythe fact that the reels from which the weblike material is unwoundfrequently present an irregular shape, for example an elliptical crosssection or in any case a deformed and non-circular cross section.

Various systems have been studied for controlling the tension of theweblike material unwound from reels. According to a first approach, theweblike material is run over a dandy roll, i.e., one supported with amobile axis of rotation, typically by means of a pair of oscillatingarms that are hinged about an axis of oscillation parallel to the axisof rotation of the roll itself. When the tension of the weblike materialtends to vary, for example on account of the irregularity of the crosssection of the reel, the dandy roll shifts, so preventing a variation oftension in the weblike material. A position transducer, for example anangular position transducer, detects the displacement of the dandy rolland generates a feedback signal, which is used by a control unit formodifying the speed of feed of the weblike material, in particular byaccelerating or decelerating the reel.

An unwinder device with a dandy roll for controlling the tension of theweblike material is described in U.S. Pat. No. 6,079,661.

This type of control is not satisfactory in that it is particularlyunstable. In fact, a possible deformation of the reel causes anoscillation of the dandy roll with a frequency of the same order ofmagnitude as the frequency of the rotation of the reel. The feedbacksignal that derives therefrom causes cyclic accelerations anddecelerations, with a similar frequency, of the speed of rotation of thereel. On account of the high inertia of the reels of weblike material,the correction made by this type of control is retarded with respect tothe onset of the variation of tension, and hence is not effective.

According to a different approach, the weblike material is run over aguiding roller, to which there are associated load cells that detect thereaction on the axis of the roll, due to the load applied on the roll bythe weblike material in tension. A possible irregularity of the crosssection of the reel tends to have repercussions in the form of aperiodic variation of the load applied on the guiding roller. Thisvariation is detected by the load cells, which generate a feedbacksignal that is used for intervening on the speed of rotation of the reelwith the purpose of making up for the oscillations in tension.

Also this solution is not satisfactory for the same reasons that renderinadequate the solution that utilizes the dandy roll, and moreoverinduce greater jumps of tension in the weblike material, even though—ascompared to the dandy-roll solution—it affords the advantage ofsimplifying the path of the weblike material.

Similar problems of control of the tension of a weblike material mayarise also in situations different from the typical one of unwindingfrom a reel for feeding a station set downstream of the stationcomprising the unwinder. In general, problems of control of the tensionof a weblike material may arise in all those situations in which theweblike material is fed from one to the other of two stations set insequence (not necessarily adjacent to one another) along a feed path,when the one or the other of the stations may undergo oscillations inthe speed of supply or of absorption of the weblike material itself.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the present invention is to provide an unwinder device,especially but not exclusively for tissue paper, which will overcome ormitigate the drawbacks referred to above.

Another object of the present invention is to provide a method forunwinding a weblike material which will overcome or reduce the drawbacksof the known methods, rendering more efficient the control of thetension of the weblike material.

More in general, the object of the present invention is to provide adevice and a method for effective control of the tension of a weblikematerial in a processing line or system, comprising at least twostations set in succession along the path of the weblike material.

According to a first and more general feature, then, the presentinvention envisages a device for controlling the tension of a weblikematerial coming out of a first station and fed to a second station of asystem, which comprises:

-   -   at least one member for regulating the speed of advance of the        weblike material along a path of advance between said first        station and said second station;    -   a central control unit;    -   along said path of the weblike material, a guiding roller with        mobile axis, over which is run said weblike material; and    -   a position transducer for detecting the position of the guiding        roller and for generating a position signal for regulating the        speed of said weblike material,        characterized in that: said guiding roller is supported in a        controlled position, and associated thereto is at least one        sensor for detecting a load applied by the weblike material on        the guiding roller; an actuator controls a controlled        displacement of the guiding roller according to a feedback        signal generated by said sensor, the actuator being controlled        so as to make up for variations of said load moving the axis of        the guiding roller; and said member for regulating the speed of        advance of said weblike material is regulated by said central        control unit, according to the position signal, so as to        maintain the axis of the guiding roller in a position that is on        average constant.

Since the guiding roller is kept in a controlled position and is not (asoccurs in traditional devices) free to move or oscillate under theeffect of the tension of the weblike material run over it, it ispossible to measure the load exerted on the roll itself by the weblikematerial and, on basis of this, to generate a feedback signal thatdetermines the displacement, which is no longer spontaneous, but insteadcontrolled, of the roll to make up for the oscillations in tension. Thecontrolled displacement of the guiding roller is continuously monitoredby means of the position transducer. Unlike what occurs in traditionaldevices, the oscillation detected by the transducer does not directlycause a variation of the speed of advance of the weblike material.Instead, the control unit performs an integration of the signal todetermine the mean position in time of the guiding roller. Only whenthis mean position departs excessively from a predetermined positiondoes it performs a correction of the speed of feed of the weblikematerial.

The member for regulating the rate of feed of the weblike material maybe a drive member or a braking member or also a combination of the twoin order to ensure a balanced control of a tensile force and of aresistant force.

Further features of the device for controlling the tension of theweblike material are specified in the attached claims.

According to a different feature, the invention relates specifically toan unwinder device, comprising:

-   -   at least one member for regulating the speed of unwinding of the        weblike material from a reel;    -   a central control unit;    -   a guiding roller with mobile axis, over which is run said        weblike material; and    -   a position transducer for detecting the position of the guiding        roller and for generating a position signal for regulating the        speed of unwinding of said weblike material.

In a device of the above type according to the invention, it isenvisaged that: the guiding roller will be kept in a controlledposition; to the guiding roller is associated at least one sensor fordetecting a load applied by the weblike material on the guiding roller;the movement of the guiding roller is controlled by an actuatoraccording to a feedback signal generated by said sensor, the actuatorbeing controlled so as to make up for variations of said load by movingthe axis of the guiding roller; and the member for regulating the speedof the weblike material is controlled by said central control unit,according to said position signal, so as to maintain the axis of theguide roller in a position that is on average constant.

With a device of this kind the regulation of the speed of unwinding ofthe reel or else of the speed of advance of the weblike material isperformed only when there is a tendency for the guiding roller to shiftaway from a mean position. Regulation is thus made on the basis of afeedback signal obtained for example by the integration in time of thepositions of the guiding roller and hence particularly stable.Notwithstanding the slowness of the possible variation of the speed ofadvance of the weblike material, the device enables accurate control ofthe tension thanks to the movement of the guiding roller, which iscontrolled in a positive way by the actuator on the basis of the tensiondetected on the material itself. The system of regulation, then,intervenes in a timely way and without any delay, thus overcoming theinertia of traditional systems that correct the position of the guidingroller by acting directly upon the speed of rotation of the reel or elseupon the rate of feed of the weblike material.

Broadly speaking, the member for regulating the speed of the weblikematerial may be a motor-driven member, which causes the unwinding of theweblike material by application of a tensile force on the materialitself in a portion in which it is already unwound, for example by meansof a pair of motor-powered drive cylinders set along the path ofunwinding of the weblike material.

Preferably, however, when the weblike material is unwound off a reel,the member for regulating the speed of the weblike material actsdirectly on the reel, axially and/or peripherically. For example, it maycomprise one or more rollers or cylinders for supporting the reel, whichby turning causes it to be unwound, or else one or more belts forunwinding set in contact with and pressed against the outer surface ofthe reel, either above it or underneath it. There may also alternativelybe provided members that transmit the necessary torque to the reelaxially, i.e. via a central spindle, or else there may be hypothesizedsolutions of a mixed or combined type. According to a differentembodiment, the weblike material may be unwound by traction force bymeans of a traction member, and the reel may be braked by means of abraking member, which is controlled by the control unit for modifyingthe rate of feed of the weblike material. In this case, therefore, themember for regulating the speed of feed of the weblike material isconstituted by a braking member, instead of by a motor-driven member.

The guiding roller may be supported in any appropriate way, providedthat it is, on the one hand, possible to keep it in a controlledposition and, on the other, movement thereof is enabled, i.e. thedisplacement of the rotation axis for modifying the path of the weblikematerial run over it, with the purpose of making up for temporallylimited variations of the tension. It may, for example, be possible touse a guiding roller mounted on slides that are mobile along arectilinear or curvilinear guide, with a position transducer fordetecting the position of the roll along the guide.

However, according to a preferred embodiment of the device forcontrolling the tension and of the unwinder device according to thepresent invention, the guiding roller is supported by oscillating armsthat oscillate about an axis of oscillation parallel to the axis of saidguiding roller.

According to a further feature, the invention relates also to a methodfor unwinding a weblike material from a reel, in which the weblikematerial is run over a guiding roller with a mobile axis of rotation andin which the speed of unwinding of the weblike material from said reelis regulated according to the displacement of said guiding roller.Characteristically, according to the invention, there is envisaged:

-   -   maintaining the guiding roller in a controlled position;    -   detecting a load applied by the weblike material upon said        guiding roller;    -   controlling, in a positive way, by means of an actuator, the        position of the axis of said guiding roller to compensate, with        a displacement of the guiding roller, for a variation of said        load; and    -   making up for the variations of the mean position of the axis of        said guiding roller by modifying the speed of unwinding of the        weblike material from the reel.

According to an advantageous embodiment of the method according to thepresent invention, there is envisaged generation of a feedback signalaccording to the load on the guiding roller and control of the movementof said guiding roller according to said feedback signal.

To obtain a stable feedback on the speed of unwinding of the weblikematerial, according to a preferred embodiment of the invention there isenvisaged: integrating the position of the axis of the guiding rollerover an interval of time; calculating the mean position of said axis;and modifying the speed of unwinding of the weblike material from saidreel to maintain the mean position within a predetermined interval.

According to a more general feature, the present invention relates to amethod for controlling the tension of a weblike material coming out of afirst section and fed along a path of advance to a second section of asystem, in which said weblike material is run over a guiding roller witha mobile axis of rotation and in which the speed of advance of theweblike material along said path is regulated according to thedisplacement of said guiding roller. Characteristically, according tothe invention, there is envisaged:

-   -   maintaining the guiding roller in a controlled position;    -   detecting a load applied by the weblike material upon said        guiding roller;    -   controlling, in a positive way, by means of an actuator, the        position of the axis of said guiding roller to make up, with a        displacement of the guiding roller, for a variation of said        load; and    -   compensating the variations of the mean position of the axis of        said guiding roller by modifying the speed of advance of the        weblike material along said path.

The invention also relates to a production line for transformation of aweblike material comprising at least two sections or stations insequence, between which there is set a device for controlling thetension of the weblike material, operating as described above.

Further advantageous features and embodiments of the invention arespecified in the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the invention will be obtained from theensuing description and from the annexed table of drawings, whichillustrate a practical non-limiting embodiment of the invention. In thedrawings, in which arts that are the same are designated by the samereference numbers:

FIG. 1 is a schematic side view of an unwinder to which there is appliedthe device according to the invention;

FIG. 2 is a block diagram of the device;

FIG. 3 is a graph plotting the trend of the angular position of thesupporting arm of the guiding roller in time in a first possible mode ofoperation;

FIG. 4 is a graph plotting the trend of the angular position of thesupporting arm of the guiding roller in time in a second possible modeof operation;

FIG. 5 is a diagram of an unwinder device according to the invention ina different embodiment;

FIG. 6 is a diagram of a generic processing line with three sections insuccession and two devices for controlling the tension, set between thesections; and

FIG. 7 is a cross section of a supporting pin for the guiding rollerwith the corresponding sensors for detection of the load applied by theweblike material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

With reference to FIGS. 1 to 4, the concept underlying the inventionwill be illustrated in an application to an unwinder device forunwinding a reel of a weblike material and feeding the material to asection set downstream of the unwinder.

FIG. 1 is a schematic illustration of a side view of a possibleunwinder, to which there is applied the device according to theinvention. The unwinder has a support 1 for a reel B of weblike materialto be unwound, said weblike material N being wound on a central core A.The support 1 comprises, in this example, a carriage that is mobile in adirection orthogonal to the plane of the figure, which is located insidea fixed structure 3, which defines a path of unwinding of the weblikematerial and on which there is supported a motor-driven member whichdrives the reel B in rotation about its own axis.

The motor-driven member is as a whole designated by 5. It is hinged in 7to the fixed structure 1 and comprises a plurality of belts 17, whichare run over rollers or pulleys 11, 13, 15, of which the pulley 11 inthe example illustrated is motor-driven by means of a motor 12. Themotor-driven member is equipped with means, which are in known per seand are not described herein, that keep the belts 17 in contact with theperiphery of the reel B.

Along the path of the weblike material N there is set a guiding roller31 supported by arms 33, which are hinged about an axis 35 parallel tothe axis of rotation of the guiding roller and fixed to the fixedstructure 3.

As shown in particular in the block diagram in FIG. 2, associated to thesupports of the roll 31 are load sensors, for example load cells, whichare designated as a whole by 37. Associated to the arms 33 is an encoderor other angular-position transducer, designated as a whole by 39,designed for detecting the angular position of the arms 33 and thecorresponding displacements about the axis 35. The arms for supportingthe roll 31 are held in a controlled position, i.e., they aresubstantially immobilized, by an actuator associated thereto. In thisway, the guiding roller is not free to oscillate under the action of thetension applied by the weblike material, and consequently the load cells37 are able to detect a force of reaction of the supports of the roll 31which is dependent upon the tension of the weblike material.

The load cells 37 and the angular-position transducer 39 are connectedto a control unit 41. This receives, then, at input from the load cells37, a signal that is proportional to the force of reaction on thesupports of the guiding roller 31, and from the transducer 39 a signalindicating the angular position of the arms 33.

The central control unit 41 is in turn connected to a motor 43 or otherappropriate actuator, which, on the one hand, keeps the arms 33 andhence the roll 31 immobilized in a controlled position and, on the otherhand, (under the control of the central control unit 41) controls themovement of oscillation of the arms 33 in the manner and for thepurposes described in detail in what follows. The central control unit41 is moreover connected to the motor 12 that controls the belts 17 ofthe motor-driven member 5, and regulates the speed of unwindingaccording to the modalities described in what follows.

In traditional systems, the guiding roller 31 moves by oscillating aboutthe axis 35 as a result of the variation of tension of the weblikematerial N, and the angular position of the arms 33, detected by theencoder or other angular-position transducer 39, determines a feedbacksignal that causes acceleration or deceleration of the motor 12 forrestoring the original position of the arms 33 and hence of the roll 31:

Instead, according to the invention, the arms 33 are kept stationaryuntil the motor 43 is actuated. A variation of the tension on theweblike material N, for example due to a deformation of the reel B,consequently causes a variation of the load detected by the load cells37. The latter generate a feedback signal according to the tensiondetected, which, by means of the central control unit 41, causes anactuation of the motor 43. In practice, the motor 43 or other equivalentactuator causes—in response to an increase or a reduction of the tensionin the weblike material N—an oscillation of the arms 33. The movement ofoscillation is not caused directly by the force applied by the weblikematerial, but rather controlled by a positive control.

If the variation in tension is, for example, a cyclic variation due toan ovalization of the reel, i.e., to an oval or elliptical shape of thecross section of the reel itself, the position of the arms 33 variescyclically, but the mean position remains substantially unvaried. Theposition signal generated by the position transducer 39 remains onaverage constant.

This situation is represented in the graph of FIG. 3, where on theabscissa there appears the time and on the ordinate a represents theangular position of the arms 33. The symbol α_(m) represents the meanposition, e.g. with the arms 33 horizontal.

A periodic oscillation like the one represented by the curve F of thetension in the weblike material causes an oscillation having a trendthat is substantially the same in the signal generated by the load cells37 and a consequent oscillation controlled positively by the motor 43,which tends to compensate this periodic variation of the tension. Theoscillation of the arms 33 is indicated by the curve α.

The angular position of the arms is detected by the angular-positiontransducer 39. If for any reason the mean position of the arms 33 tendsto vary, departing from the mean position α_(m), this circumstance isdetected by the central control unit 41, which on the basis of theposition signal coming from the transducer 39 generates a control signalfor the motor 12. The signal is such as to cause a gradual accelerationor a gradual deceleration of the belts 17 and hence of the reel B tomake up for the drift of the mean position of the arms 33 with respectto the pre-set mean position α_(m).

The graph of FIG. 4 is a schematic representation of a situation thatcalls for the intervention of the correction on the speed of rotation ofthe motor 12 and hence of the reel B. As may be noted from the graph,the mean value of the curve a varies in time. The ratio between theintegral of the function α(t) and the integration time interval does notremain constant, but rather (in the example illustrated) tends toincrease.

Assuming that the angle α is measured in the clockwise direction, whenthe mean value exceeds an upper threshold value α_(s1), the deviceintervenes with an acceleration of the motor 12. This causes a graduallowering of the mean position of the arms 33 until the pre-set meanposition α_(m) is reached. When the lower threshold value α_(s2) isoverstepped, this causes an opposite reaction of the system, with adeceleration of the motor 12 and hence of the reel B.

From the above description, it may be readily understood that thecontrol performed in this way enables a reduction to a minimum of theinterventions of acceleration or deceleration of the reel B and aboveall enables a variation in the angular velocity of the reel, which isvery slow, with consequent advantages in terms of inertia. The system isstable in so far as any periodic oscillations of the tension in theweblike material are compensated for by the motor 43, withoutinterventions on the speed of unwinding of the weblike material, whereasonly when the mean position of the arms 33 tends to depart from thepre-set value is it necessary to intervene, with adequately long timeintervals, on the speed of rotation of the reel B.

FIG. 5 illustrates a diagram, similar to the diagram of FIG. 2, of anunwinder device in which the unwinding of the reel B is obtained byapplication of tensile force on the weblike material and in which thespeed of advance of the weblike material is regulated by means of abraking member instead of by means of a motor-driven member. Parts thatare the same or are equivalent are designated by the same referencenumbers as those adopted in FIG. 2. The unwinder 5 comprises, in thiscase, a braking member designated by 12X, which applies a braking torqueon the axis of the reel B. The braking member 12X is connected to thecentral control unit 41. The weblike material is unwound by exertion ofa tensile force by means of a pair of motor-powered drive cylinders 14,which are driven by means of a motor drive 16. Also the latter may beinterfaced to the central control unit 41. The drawing of the weblikematerial may be obtained also by means of the members of the machine orstation that is located downstream of the unwinder, instead of by meansof a purposely provided pair of motor-powered drive cylinders. Thedevice operates in a way similar to what has been described previously,with the difference that the possible deviation of the mean position ofthe arms 33 from a pre-set position determines, by means of the centralcontrol unit 41, a control signal to the braking member 12X, whichmodifies the resistant torque applied for reducing or increasing thespeed of feed of the weblike material N, according to the samemodalities described previously.

FIG. 6 is a highly schematic illustration of a further application ofthe principle underlying the present indention, to a generictransformation line, designated by with 51 and comprising three genericsections 53, 55, 57 set in sequence along the path of the weblikematerial N. Each section 53, 55, 57 may comprise any type of machinerythat operates at a fixed or variable speed on the weblike material N.Set between the stations or sections 53, 55 and between the sections 55and 57 are respective devices for controlling the tension of the weblikematerial, which are designated by 61 and 63. Each of said devicescomprises a pair of oscillating arms 33, which support respectiveguiding rollers 31 of the weblike material N. Each pair of arms is heldin an angular position controlled by an actuator 43, and the angularposition is detected by a transducer 39. Associated to the supports ofthe rollers 31 are load cells 37 for detecting the force of reactionapplied on the rollers 31 by the weblike material.

The load cells associated to the two rollers 31, as well as therespective position transducers 39 and the actuators 43 are interfacedto a central control unit 41, to which are connected also the threesections 53, 55, 57 of the line 51. By means of the actuators 43 thecentral control unit controls, according to the signals coming from theload cells 37, the movement of oscillation of the rollers themselves formaintaining the tension constant, according to the same proceduredescribed with reference to the unwinder of FIGS. 1 to 4. The meanposition in time of the arms 33 is calculated by the central controlunit 41, which consequently may generate (if necessary) a signal forcorrection of the output speed of the weblike material from the sectionupstream or of input speed of the weblike material in the section setdownstream with respect to the control device 61, 63, the guiding rollerof which is moving away, as regards the mean position, from the pre-setposition.

The control devices 61, 63 may also have the function of maintainingconstant the tension of the weblike material in the respective stretchof the feed path when the section upstream delivers the material itselfat a substantially constant speed, and the section set downstreamabsorbs the weblike material with a cyclic variation of speed, or viceversa. In this case, the cyclic variation of the tension of the weblikematerial deriving from the variation of the speed with which the weblikematerial is absorbed by the section set downstream (or delivered by thesection set upstream) is compensated for by the controlled oscillationof the corresponding guiding roller, without modifying the constant orsubstantially constant rate of output of the weblike material by theupstream section (or the speed of absorption of the downstream section).

FIG. 7 is a schematic illustration of an embodiment of one of the twoend supports of the guiding roller 31 in any of the embodiments so fardescribed. The support is formed by a pin 101 constrained to therespective arm 33 and on which there is fitted a bearing 103 forsupporting the guiding roller 31. The pin 101 has a transverse throughhole 105, orthogonal to the axis of the pin itself and with an axisorthogonal to the direction of the resultant F of the forces applied bythe supporting bearing 103. Set inside the hole 105 are two load cellsarranged opposite to one another, designated by 37A and 37B. Theorientation of the resultant F with respect to the axis of the hole 105and to the position of the load cells 37A, 37B is such that the latterare able to detect even very small flexural deformations of the pin 101due to the variation of the resultant force F, and hence in practice ofthe tension on the weblike material.

It is understood that the table of drawings illustrates only a practicalembodiment of the invention, which may vary in the forms andarrangements, without thereby departing from the scope of the conceptunderlying the invention. The possible presence of reference numbers inthe annexed claims merely has the purpose of facilitating readingthereof in the light of the foregoing description and of the attacheddrawings and in no way limits the scope of protection defined by theannexed claims.

1. A control device for controlling tension of weblike material coming out of a first station and fed to a second station of a system comprising: at least one member for regulating speed of advance of said weblike material along a feed path between said first station and said second station; a central control unit; along said path of the weblike material, a guiding roller with mobile axis over which is run said weblike material; and a position transducer for detecting position of the guiding roller and for generating a position signal for controlling the speed of said weblike material; wherein said guiding roller is supported in a controlled position and associated therewith is at least one sensor for detecting a load applied by the weblike material on the guiding roller; an actuator for controlling displacement of said guiding roller according to a feedback signal generated by said sensor, the actuator being controlled so as to make up for variations of said load moving the axis of the guiding roller; and said member for regulating the speed of advance of said weblike material is controlled by said central control unit, according to the position signal to maintain the axis of the guiding roller in a position that is on average constant; wherein said control unit determines, based on the position signal coming from said transducer, trend in time of the position of the axis of said guiding roller; and said control unit causes, by means of said member for regulating the speed of advance of the weblike material, a variation of the speed of the weblike material when a mean value of said position exceeds a threshold value from a pre-set mean position (α_(m)).
 2. The device according to claim 1, wherein said member for regulating the speed of advance of said weblike material is a drive member which applies a driving force upon the weblike material.
 3. The device according to claim 1, wherein said member for regulating the speed of advance of said weblike material is a braking member which applies a braking force upon the weblike material.
 4. The device according to claim 1, wherein said member for regulating the speed of advance of the weblike material acts upon a reel on which said weblike material is wound and from which said weblike material is unwound at a tension controlled by said device.
 5. The device according to claim 1, wherein said guiding roller is supported by oscillating arms that oscillate about an axis of oscillation parallel to the axis of said guiding roller; said position transducer detects angular position of said arms; and said actuator controls oscillation of the arms about said axis of oscillation.
 6. The device according to claim 1, wherein said sensor for detecting the load applied on the guiding roller by the weblike material is associated with the support of the guiding roller.
 7. The device according to claim 1, further comprising two sensors applied to two supports of the guiding roller.
 8. The device according to claim 1, wherein said at least one sensor for detecting the load applied on the guiding roller is a load cell.
 9. The device according to claim 5, said position transducer is an angular-position transducer.
 10. An unwinder device comprising at least one support for a reel of weblike material to be unwound and to be supplied to a station set downstream of said unwinder along a system, comprising a control device for controlling tension of the weblike material unwound from said reel, according to one of claims 1-9.
 11. A method for controlling tension of a weblike material coming out of a first section and fed along a path of advance to a second section of a system, wherein said weblike material is run over a guiding roller with a mobile axis of rotation, and wherein speed of advance of the weblike material along said path is regulated according to displacement of said guiding roller, comprising: maintaining said guiding roller in a controlled position; detecting a load applied by the weblike material (N) upon said guiding roller; positively controlling, by means of an actuator, position of the axis of said guiding roller to make up, with a displacement of the guiding roller, for a variation of said load; making up for variations of a mean position of the axis of said guiding roller by modifying the speed of advance of the weblike material along said path; wherein integrating the position of the axis of the guiding roller over an interval of time; calculating the mean position of said axis; and modifying the speed of advance of the weblike material along said path for maintaining the mean position within a predetermined interval.
 12. The method according to claim 11, wherein a feedback signal is generated according to said load and movement of said guiding roller is controlled according to said feedback signal.
 13. The method according to claim 11 or 12, wherein the axis of the guiding roller is angularly mobile about an axis of oscillation.
 14. The method accordingly to claim 11, wherein said weblike material is unwound from a reel in said first station.
 15. The method according to claim 14, wherein the speed of advance of the weblike material is modified by acting upon a motor-driven member which drives in rotation said reel.
 16. A line for transformation of a weblike material comprising at least a first station and at least a second station set in sequence along a path of advance of the weblike material; with means for controlling tension of the weblike material along said path of advance, comprising at least a control device for controlling the tension of the weblike material according to one of claims 1-9.
 17. The line according to claim 16, further comprising an unwinder in said first station, the control device for controlling the tension of the weblike material controlling the tension of the weblike material unwound from said unwinder.
 18. The line according to claim 17, wherein set downstream of said unwinder there is provided a station comprising a rewinder. 